Hello @danisabad ,
Regarding my experience I can tell you that there is on the admin panel a notification tab which has all the possible notifications shared from the gallery directly to users.
In this cases, only workflows shared with you will be notified and not if the total amount of workflows has been increased.
For that I would recommend you creating a workflow with the mongodb input and save on an yxdb the current amount of workflows your gallery has. Then run this workflow on a daily or hourly basis, depending on your needs and use a join tool to compare the amount from the yxdb table with the one from the mongodb.
This is the only way that comes to mind for doing such a task.
Regards